Sequestrate Industrial Waste Gas For Preparing Building Materials By Steel Slag And Paper Sludge

Steel slag, a kind of industrial residues, is generated in the process of steel-making. With the quick development of steel industry, the amount of steel slag increase quickly. Due to amount of complicate composition, especially some of free-calcium oxide and free-magnesium oxide which affect the stability of steel slag products, so the application of steel slag is limited. In addition it could take up a lot of land and pollute the environment.Paper sludge is the final material which origins from the treatment of liquid waste. Regardless of landfill, incineration or ocean disposal, there are secondary pollution, power source consuming and space holding in the treatment of paper sludge, so paper sludge couldn't be treated usefully.CO₂ sequestration by minerals, namely greenhouse gas CO₂ reacting with non-carbonate minerals to form geologically stable mineral carbonates, such as CaCO₃, MgCO₃, is carbonation. As an advanced technology, carbonation utilizes the waste and saves resources and energy; carbonation could be a technique to tackle with steel slag and paper sludge effectively. The pollution of steel slag and paper sludge will not only be solved, but also ease the greenhouse effect caused by carbon dioxide.Based on the experimental results, effects of Ca(OH)₂ content, forming pressure, CO₂ partial pressure and carbonation time on the carbonation were analyses by some theories. Comprehensive strength, soundness, molding ease and cost were considered, and determine the optimum Ca(OH)₂ content was 12% and 8% for fine and coarse steel slag respectively, optimum molding pressure was 7 MPa, and samples were carbonated in three phases for 3 h, CO₂ partial pressure was 0.15 MPa, 0.25 MPa and 0.3 MPa respectively in each phase.Research the carbonation manchine of steel slag. After 24 h hydration, the cumulative release heat of steel slag was 30 J / g, while after 60 min carbonation; this value reached 95 J / g. The Ca(OH)₂, f-CaO, C₂S and C₃S and other minerals in the steel slag can be chemical reacted with CO₂ gas, and 121.8 g carbon dioxide could be sequestrated each kg of steel slag through carbonation. The pore rate of samples fell form 21.76% to 13.34% when carbonation 60 min, while the compressive strength of samples increased form 6.69 MPa to 42.14 MPa, and f-CaO content in steel slag decreased markedly, what's more, the carbonated samples had good soundness.Coarse slag powder was used to optimize the bulk density (from 2.07～2.42 g/cm³ to 1.86 g/cm³) and performances of steel slag products. When the carbonation weight gain of this samples was 5.52%, the bending strength was 4.12 MPa, the compressive strength was 15.39 MPa, soundness was qualified, the frost resistance was eligible (after 15 freeze-thaw cycles, freezing and thawing strength was 5.39 MPa), the water absorption was 16.27% and the saturated intensity was 5.74 MPa, which all meet certain national standards, the optimum weight ratio of samples was fine steel slag powder 10%, coarse steel slag powder 35%, steel slag particle 5% and slag particle 50%.Common building materials such as cement, lime, steel slag and other materials were used for experiments, and steel slag mixed with paper sludge was determined to sequestrate greenhouse gas for preparing building materials. Carbonation steel slag mixed with paper sludge system was research based on steel slag exploration, and the effects of Ca(OH)₂ content, forming pressure, CO₂ partial pressure and carbonation time on the carbonation were analyses by some theories. Comprehensive strength, carbonation weight gain and cost were considered, and determine the optimum Ca(OH)₂ content was 17%, carbonation temperature was 60℃, and samples were carbonated in two phases for 1.5 h, CO₂ partial pressure was 0.10 MPa and 0.30 MPa respectively in each phase.Under optimal conditions, the mixed designation of paper sludge which may influence the carbonation effect was explored. XRD, SEM-EDS, DTA-TG and other testing methods were used to analysis the composition, morphology and thermodynamics character of carbonated products. Experimental results show that the effect of carbonation is much better when the percentage of paper sludge is 20 wt%. A great deal of granular crystal of calcium carbonate was appeared in carbonated products, and their structure is more compact and uniform. Compression strength of test sample was 13.87 MPa, and flexural strength was 3.89 MPa, hygroscopic coefficient was 12.93 wt%, density was 2.46 kg/m³, soundness was qualified.